To demonstrate how rain affects topsoil.
Red powdered tempera paint
Measuring spoon, teaspoon (5 ml)
Coffee filter paper
Wide mouthed jar, 1 qt. (1 liter)
Measuring cup, 1 cup (250 ml)
ProcedureAdd 1¼ teaspoon (1.25 ml) of red tempera paint to 114 cup (75 ml) of dirt.
Set the funnel in the jar.
Place the coffee filter inside the funnel.
Pour the colored sand into the paper filter.
Add 1¼ (75 ml) of water to the funnel.
Observe the water dripping into the jar.
Pour this water out of the jar and add another 1¼ cup (75 ml) of water to
The liquid dripping out of the funnel is red.
The red paint represents nutrients in topsoil that are soluble in water.
Nutrients dissolve in rainwater and feed the plants growing in the soil. If the
rain is too heavy, the water runs across the land, taking the dissolved
nutrients with it. Excessive rains can leave the topsoil lacking in necessary
Printed with permission from Michal L. Le Vasseur, 2001
Runoff (Adobe PDF document)